In a rare speech late on Sunday night, the Syrian president, newly buoyant from his victories against the rebels in the central city of Homs, deemed his political opposition a “failure” and said his army would crush “terrorism”, referring to the country’s insurgency.

“No solution can be reached with terror except by striking it with an iron fist,” he said, in remarks carried by the Syrian state news agency SANA.

His speech came as reports emerged Monday night of a ‘toxic gas’ in the air wounding ‘hundreds’ as it drifted across the Damascus suburb of Douma. Video footage showed men and women in civilian clothes in a hospital covering their mouths with cloth, choking.

The activist Local Coordination Committee said that “hundreds suffered from asphyxiation after the city was attacked with chemical weapons and poisonous gas.”

The opposition Local Coordiantion Committee in the area accused the regime of launching a ‘chemical weapons attack’ on the district, whose population has been largely sympathetic to the opposition and was, for a short time in rebel hands.

Other local residents told the Telegraph that the toxic gas may be the result of a regime airstrike on a nearby gas plant, though there was some confusion surrounding the order of the events: “After the rebels took over gas plant at Adra, the regime bombed it, sparking a large fire that spread toxic gas across the area,” said an activist calling himself Mohammed al-Douma, speaking by Skype from the area.

Mr Assad’s uncompromising message will come as a disappointment to Western diplomats and United Nations officials who have been rallying the Syrian government and the opposition to peace talks in Geneva.

Western officials have told The Daily Telegraph the talks are the central tenet of Britain’s response to the Syrian crisis, with hopes that Russia and the United States might, on this rare occasion, work together to pressure both sides to negotiation. Mr Assad’s latest statement now makes that ambition seem even more far-fetched.

The Syrian president spoke while attending a Sunday evening “iftar” or meal to break the daily fast during the holy Muslim month of Ramadan.

“There can not be political action and progress on the political track while terrorism hits everywhere,” he told prominent members of Syria’s clergy, business and arts community. “Terrorism and politics are complete opposites.”

The Syrian president mocked the Syrian National Coalition, the Western-backed opposition, as being morally bankrupt and “unpatriotic”, chasing positions of power, changing its stance regularly and receiving Gulf money.

In past months the Syrian army, supported by militias funded by Iran and Iraq, has made a series of military gains, pushing rebel groups from much of the centre of the country.

Mr Assad’s appearance, which has been rare in the past two years, seems part of a coordinated campaign to build on these victories, putting the president, and his British-born wife, Asma al-Assad, back into the Syrian public limelight.

Most recently, the First Lady is pictured in a pale blue shirt stirring the contents of a large pot, at a volunteer evening to give food to internally displaced citizens.

The brutal reality of the war, that has now claimed more than 100,000 lives, and for which the Syrian president is wanted by UN investigators on charges of war crimes is imperceptible in the presidential PR campaign.

The new report by Human Rights Watch found that the Syrian regime is firing high explosive, ballistic missiles into population centres where rebel groups may be hiding, with no apparent concern for civilian residents.

An investigation of nine different sites by the watchdog found that 215 people, including 100 children have been killed in ballistic missile attacks between February and July of this year alone.

Ole Solvang, senior emergencies researcher at Human Rights Watch said: “Even if there are fighters in the area, you cannot accurately target them and the impact in some of these cases has been devastating to local civilians.”